30 minutes is a very short period of time, so you have to choose your materials wisely. Generally speaking, you should give the audience a big picture of the presented topic, then emphasize on a few selected points that you consider the most important.

The purpose of a presentation is to convey certain idea, concept, or knowledge to the audience, therefore it is important that the presentation be organized in a way so that the audience can easily follow, understand, and remember. A recommended "template" for a presentation is as follows:

• Introduction, which may include background information and motivating examples to show why the audience should care about the topic you are going to present.
• Overview of the topic, or in other words the "big picture", e.g. the system architecture of your project.
• Technical details. Again, focus on a few things you want the audience to take away with them at the end of the talk.
• Results, such as experiments, performance comparisons, and demos.
• Summary, conclusion, and/or future work.

Use non-distracting colors, font types, and layouts.

The slides should show the outlines and highlights of your talk, not the whole talk itself. Do not write an article on a slide.

Animation in particular is a good way to help illustrate a complex/dynamic process.

Stand straight and face the audience (not the screen). Speak clearly and confidently, and make sure that your voice is loud enough so the audience in the back rows can hear you.

Do not speak too fast, so the audience have time to digest what you said. Give short, to-the-point answers to the audience's questions. Always pay attention to audience reactions, e.g. whether they look bored or confused, and adjust your talk accordingly.

Keep the time of your presentation between 25 minutes and 35 minutes. Generally speaking, you need to prepare about 20 slides, and spend about one or two minutes on each slide. If the audience ask a lot of questions, you may need to skip some less important content.